Paleoecotoxicology of smelting-affected lakes near Sudbury (Ontario, Canada)
Bibliographic record
Abstract
For over a century, Sudbury (Ontario, Canada) has been a major copper-nickel metal smelter centre. Emissions of acidifying compounds and metal particulates beginning in the 1880s damaged thousands of lakes and watersheds in the region. Emission controls introduced in the 1960s and 1970s greatly affected water chemistry. Despite evidence of chemical recovery, comparatively little is known about long-term changes in aquatic biota of affected lakes. Here, I use three paleolimnological approaches to assess spatial and long-term temporal trends in cladocerans (Branchiopoda: Cladocera) and chironomids (Diptera: Chironomidae). First, a survey of >60 lakes revealed that recent cladoceran assemblages were related to lakewater specific conductance in combination with nutrients, alkalinity, and lake depth, whereas recent chironomid assemblages are structured primarily by lake depth and secondarily by copper and calcium concentrations. Second, a comparison of recent and pre-industrial sediments using a “top-bottom approach” demonstrated that both cladoceran and chironomid assemblages changed modestly. Acid- and metal-tolerant taxa were more common in recent sediments. In cladoceran assemblages, the Daphnia longispina complex was partially replaced by the D. pulex complex, which was more tolerant of low-calcium conditions in our focal lakes; further modern zooplankton monitoring may refine this interpretation by determining which species are represented in the morphological species complexes in sediment records. For both indicators, early colonist taxa were more common in recent sediments. I also found that recent cladoceran assemblages clustered spatially, which may be the result of historical contamination and modern stressors. Finally, I examined four lakes with varying environmental histories to compare recovery trajectories, establish baseline conditions, and assess biotic changes during peak emissions. Lake acidification and metal contamination altered all proxies in acid-sensitive lakes. The most consistent changes in invertebrate assemblages were the loss of littoral/sub-littoral taxa during acidification, the replacement of acid-/metal-sensitive taxa with tolerant assemblages, and the lack of recovery in recent sediments. Overall, these results suggest that cladoceran and chironomid assemblages responded to historical smelting activities, with limited biological recovery to pre-industrial conditions. Placing recovery trajectories in the context of modern environmental stressors, such as recent climatic change, will continue to be important for future mitigation efforts.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".